Transcript Lesson 4 Layout Design Techniques:

Lesson 4 Layout Design Techniques:
Line Balancing
Last Week
 Discussed volume & variety
 Processes – Project, Jobbing, batch,
mass & continuous
 Looked at layouts - Fixed position,
cellular, process and product
This Week

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
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Layout Design Techniques
Focus on Product layout
Cycle time
Line Balancing
Product Layout
 Transforming resources located for the
convenience of the transformed
resources
 Product/customer/information follow a
pre-arranged route
 Sequence of activities matches the
sequence in which process’s have been
located
Detailed Design - Product Layout
 Key decisions are concerned with ‘what to
place where’ – in terms of what to allocate to
each of the workstations.
 This is termed line balancing
 Other key questions are:
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What cycle time is needed?
How many stages are needed?
How should the layout be balanced?
How should the stages be arranged?
Some definitions – (ch4 Slack)
 Cycle time – the average time for units of
output to emerge from the process
 Throughput time – the time for a ‘unit’ to
move through the process
 Work Content – the total amount of work
required to produce a unit of output
 WIP – work in progress
Detailed Design - Product Layout
Cycle time = time available
No.of units to be processed
 Suppose a bank is designing an operation to process
mortgage applications. The number to be processed per
week= 160 and the time available for processing = 40
hours
Cycle time = 40 = 1 hr = 15 minutes
160 4
Detailed Design - Product Layout
Number of stages req. = work content
required cycle time
Suppose the back in the previous example calculated the total
work content to process a mortgage application to be 60
minutes. Cycle time = 15 mins
Number of stages = 60 = 4 stages
15
Detailed Design - Product Layout
 The previous example assumed that 15mins. of work time
was allocated equally to each of the 4 stages.
 This can be almost impossible in practice and some
imbalance results
 The effectiveness of the line balancing is measured by
‘balancing loss’
 Balancing loss - is that proportion of the time invested in
processing the product or service which is not used
productively
 Can lead to excessive stations being required
Calculation of Balancing Loss
An ideal ‘balance’ where work is
allocated equally between the stages
3
But if work is not equally allocated the
cycle time will increase and
‘balancing losses’ will occur
Cycle time = 2.5 mins
3.5
3
3.0
2.5
2
Load
Load
2.5
Cycle time = 3.0 mins
1.5
1
2
2.3
2.3
2.5
2.5
2.2
2.2
3.0
1
2
3
4
1.5
1
0.5
0.5
0
1
2
3
Stage
Work allocated to stage
Idle time
4
0
Stage
Calculating balancing loss:
Idle time every cycle =(3.0 - 2.3) + (3.0 - 2.5) + (3.0 - 2.2)
= 2.0 mins
Balancing loss
= 2.0
4 x 3.0
= 0.1667
= 16.67%
The Plug and Play Excercise
STAGE 1
STAGE 2
STAGE 3
STAGE 4
(10 secs)
(50 secs)
(15 secs)
(15 secs)
1. WHAT WAS THE CYCLE TIME?
2. HOW LONG DID IT TAKE TO MAKE THE FIRST PLUG?
3. HOW LONG DID IT TAKE TO MAKE THE LAST PLUG?
Timing diagram
START OF
PRODUCTION
STAGE 1
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
10
20
30
40
50
60
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100
110
120
130
140
150
160
10
20
30
40
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160
10
20
30
40
50
60
70
80
90
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110
120
130
140
150
160
STAGE 2
STAGE 3
STAGE 4
90 secs
50 secs
Start up
First Plug Produced
Second Plug Produced
Timing diagram
END OF
PRODUCTION
STAGE 1
10
20
30
40
50
60
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90
100
110
120
130
140
150
160
10
20
30
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160
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20
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140
150
160
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
STAGE 2
STAGE 3
STAGE 4
50 secs
50 secs
Plug Produced
50 secs
Plug Produced
Last Plug Produced
Detailed Design - Product Layout
 In Line balance calculations the initial
start up situation is neglected and the
cycle time is taken as the continuous rate
of output
 In this case 1 plug every 50 seconds
 Note – it is the value of the longest
activity (the bottleneck)
 Using this value the line balancing loss
can be calculated
The Plug and Play Excercise
STAGE 1
STAGE 2
STAGE 3
STAGE 4
(10 secs)
(50 secs)
(15 secs)
(15 secs)
Idle time = (50-10)+0+(50-35)+(50-35)
CYCLE TIME = 50 secs
= 40+0+35+35 = 110 secs
WORK CONTENT = 90 secs
Balance loss = (110/4*50)*100 = 55%
60
Stage 1
Stage 2
10 secs
50 secs
50
Fit pins to plug
Get plug from stage 1
10secs
Fit screws and cable retainer 30 secs
Take plug to Stage 3
Stage 3
15 secs
Fit fuse and holder
Stage 4
15 secs
Inspect and fit top cover
10 secs
40
40
35
35
30
20
10
0
1
2
3
4
Karlstad Kakes Exercise
Consider Karlstad Kakes (KK) a manufacturer of speciality
cakes which has recently obtained a contract to supply a
major supermarket chain with speciality cake in the shape
of a space rocket. It has been decided that the volumes
required by the supermarket warrant a special production
line to perform the finishing, decorating and packing of the
cake. This line would have to carry out the elements in the
precedence diagram shown on the next slide.
The initial order from the supermarket is 5000 cakes a
week and the number of hours worked by the factory are
40 hrs/week
Element listing and precedence diagram for
Karlstad Kakes
0.17 mins
e
PRECEDENCE
DIAGRAM
0.25 mins
0.30 mins
a
0.12 mins
b
c
d
0.05 mins
0.25 mins
f
g
0.36 mins
i
0.10 mins
h
0.08 mins
Element
No of units required - 5000 cakes per week
Time available - 40 hrs per week
Cycle Time = 40x60/5000 = 0.48 mins
Element
Element
Element
Element
Number
of stages
= work content/ cycle time
Element
= 1.68/0.48 = 3.5
Element
Element
Element
ab
c
d
e
f
g
h
i
- De-tin and trim
0.12 mins
- Reshape with off-cuts
0.30 mins
- Clad in almond fondant
0.36 mins
- Clad in white fondant
0.25 mins
- Decorate, red icing
0.17 mins
- Decorate, green icing
0.05 mins
- Decorate, blue icing
0.10 mins
- Affix transfers
0.08 mins
- Transfer to base and pack
0.25 mins
Total work content = 1.68 mins
Allocation of elements to stages
and balancing loss for Karlstad Kakes
Stage 1
Stage 2
Stage 3
0.17 mins
Stage 4
e
0.25 mins
0.30 mins
a
b
c
0.12 mins
0.36 mins
d
0.05 mins
0.25 mins
f
g
i
0.10 mins
h
0.08 mins
MAXIMUM CYCLE TIME = 0.48 minutes
0.6
0.5
Cycle time = 0.48 mins
0.4
0.3
0.42
0.36
0.42
0.48
1
2
3
4
0.2
0.1
0
BUT MUST NOT COMPROMISE
PRECEDENCE
Idle time every cycle = (0.48 - 0.42) + (0.48 - 0.36) + (0.48 - 0.42) - 0 = 0.24 mins
Proportion of idle time per cycle = 0.24 = 12.5%
4 x 0.48
Stage Arrangement
 How could the Plug and Play scenario be
improved?
LONG AND THIN
Stage 1
Stage 2
10
50
Stage 3
15
Stage 4
One plug every 50
secs
15
SHORT
LONG AND
ANDTHIN
FAT
More flexible
Controlled
flow
–
More efficient
Volume
-as demand
– In real
varies
situation
shut down
build
individual stages
operations
are more complex. If each
stage is performing a small part of the
Mix – Individual stages can specialise
job can be made highly productive
Highly Robust
through
the elimination
– Any oneofstage
wastefails
time
other three carry on
Less Monotonous work
90
Stage 1
90
Stage 2
90
Stage 3
90
Stage 4
One plug every
22.5 secs
SHORT AND FAT
Stage Arrangement
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Two main options:
 Long thin line
 Short fat line
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Advantages of long thin:
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Easy to manage flow of materials
Simplified material handling
More efficient operation
Advantages of short fat:
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Higher mix flexibility
Higher volume flexibility
Higher robustness
Less monotonous work
Next Week
 Answer SAQ for Unit 1 - Lesson 4
ready for tutorial sessions on Monday
29TH October
LAYOUT DESIGN TECHNIQUES –
PRODUCTION FLOW ANALYSIS
Tutorials
Room RV307
 Group 1 11-0 to 11-35pm
 Group 2 11-40 to 12-15 pm
 Group 3 12-25 to 13-0pm
 See list to find out which group you
are in
Line Balancing Exercise

SMC Ltd are developing a new process. The process has the
following tasks and linkages.
Activity
Time (sec)
Predecessor
A
12
B
8
C
10
D
16
C
E
20
B,D
F
9
G
15
H
11
E,F,G
I
8
H
J
15
I
K
8
I
L
13
J,K
A
[adapted from Martinich, 1997]
Line Balancing Exercise
 Your task is to :
 Calculate the max cycle time if 1100 units
are to be produced/8 hour day.
 Calculate the minimum number of
workstations.
 Design a line that minimises the number
of workstations.
 Calculate the actual cycle time,
production rate and efficiency
Self Assessment Questions
Line Balancing Case Study
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Read the Weldon Case study on pgs 240-241.
Working in groups of 2-3 answer the following
questions:
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How many people will be needed to assemble
the product, during (i) yr1 qtr 1 and (i) yr2 qtr
4. Comment upon the sales forecast profile.
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Design a layout for production during yr 1 qtr 1,
consider both the short fat and long thin
options. Discuss the arguments associated with
each model.